Learn Hardcore Dutch: Bij die halte stappen veel passagiers in met zware tassen. - At that stop many passengers get on with heavy bags.

Bij die halte is a prepositional phrase meaning “at/near that stop.” In Dutch, bij indicates location at or near something (e.g. bij de supermarkt, bij het station). You don’t say op de halte in this context—op would be used for surfaces (“on the table”), not for bus/tram stops.

Why is the verb instappen split into stappen … in?

Instappen is a separable verb composed of the stem stappen (“step”) plus the prefix in (“in/board”). In main clauses, the prefix detaches and moves to the end:
→ Veel passagiers stappen in (“Many passengers board”).
In subordinate clauses it stays attached: dat ze instappen.

Why is it stappen and not stapt?

The subject veel passagiers is plural. In Dutch, third person plural verbs take the bare infinitive ending -en (zij stappen), whereas third person singular takes -t (hij stapt).

Why use die halte instead of de halte or deze halte?

Die is the distal demonstrative for de-words (common gender).
• die halte = “that stop” (something already mentioned or farther away)
• de halte = “the stop” (neutral)
• deze halte = “this stop” (closer or just pointed out)

Why doesn’t veel passagiers have an article?

Quantifiers like veel, enkele, weinig directly modify nouns without an article. You say veel mensen (“many people”), not de veel mensen. If you wanted “many of the passengers,” you’d say veel van de passagiers.

Why does zware tassen have an -e on zware?

Adjectives before plural nouns (and before de-words with any article or demonstrative) take the weak inflection -e. So you get zware tassen (“heavy bags”). Only with an indefinite neuter singular noun (het-word without article) does the adjective stay uninflected: e.g. zwaar glas (if glas were used generically).

Could met zware tassen appear elsewhere in the sentence?

Yes. Because instappen is separable, you can insert prepositional phrases between stappen and in:
→ Bij die halte stappen veel passagiers met zware tassen in.
The meaning stays the same; you’re just shifting the adverbial.

What word-order rule explains the sentence structure here?

Dutch main clauses follow the V2 (verb-second) rule: the finite verb must occupy the second position. In your sentence:
1) First position: Bij die halte (fronted adverbial)
2) Second position: stappen (finite verb)
3) Third position: veel passagiers (subject)
… then the object/adjuncts, and finally the separable particle in.